Hi Vis Panels
The Royal Air Force is currently experimenting with orange dayglo panels at two spanwise locations (each panel approx 1m square) on the wings of its glider fleet (as used by the Air Training Corps). I have been flying in and around these aircraft with these panels for a while and in my opinion they do make it easier to spot white aircraft in some ways. What they do not do is make a gliders front or rear profile any larger which, when talking about spotting gliders from a distance is really the problem! Maybe a reflective foil type material along the leading edges of the wings might make a significant difference with little or no loss in aircraft performance.
The whole idea of gliders flying in controlled airspace is, in my opinion a dubious one - they just do not have the freedom to do what they are told. How can we get into a situation where a controllers actions force a glider into a field with the corresponding increased safety risks. At present I think that the vast majority of glider pilots give radio controlled airspace a wide berth and regardless of any future airspace restrictions thats the way it will stay for a long time.